Re: ppc: RECLAIM_DISTANCE 10?

[David Rientjes]

On Wed, 19 Feb 2014, Michal Hocko wrote:

> Interesting. So is the PPC NUMA basically about local vs. very distant?

The point is that it's impossible to tell how distant they are from one 
NUMA domain to the next NUMA domain.

> Should REMOTE_DISTANCE reflect that as well? Or can we have 
> distance < REMOTE_DISTANCE and it would still make sense to have
> zone_reclaim enabled?
> 

Ppc doesn't want to allocate in a different NUMA domain unless required, 
the latency of a remote access is too high.  Everything that isn't in the 
same domain has a distance >10 and is setup as 2^(domain hops) * 10.  We 
don't have the ability like with a SLIT to define remote nodes to have 
local latency vs remote or costly latency so the safe setting is a 
RECLAIM_DISTANCE of 10.
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